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| 1 | +/** |
| 2 | + * https://leetcode.com/problems/two-sum |
| 3 | + * time complexity : O(m x m) |
| 4 | + * space complexity : O(m x n) |
| 5 | + */ |
| 6 | +function pacificAtlantic(heights: number[][]): number[][] { |
| 7 | + const m = heights.length; |
| 8 | + const n = heights[0].length; |
| 9 | + const pacific: boolean[][] = Array.from({ length: m }, () => Array(n).fill(false)); |
| 10 | + const atlantic: boolean[][] = Array.from({ length: m }, () => Array(n).fill(false)); |
| 11 | + |
| 12 | + const directions = [[1, 0], [-1, 0], [0, 1], [0, -1]]; |
| 13 | + |
| 14 | + function dfs(r: number, c: number, visited: boolean[][], prevHeight: number) { |
| 15 | + if (r < 0 || c < 0 || r >= m || c >= n || visited[r][c] || heights[r][c] < prevHeight) { |
| 16 | + return; |
| 17 | + } |
| 18 | + visited[r][c] = true; |
| 19 | + for (const [dr, dc] of directions) { |
| 20 | + dfs(r + dr, c + dc, visited, heights[r][c]); |
| 21 | + } |
| 22 | + } |
| 23 | + |
| 24 | + for (let i = 0; i < m; i++) { |
| 25 | + dfs(i, 0, pacific, heights[i][0]); |
| 26 | + dfs(i, n - 1, atlantic, heights[i][n - 1]); |
| 27 | + } |
| 28 | + for (let i = 0; i < n; i++) { |
| 29 | + dfs(0, i, pacific, heights[0][i]); |
| 30 | + dfs(m - 1, i, atlantic, heights[m - 1][i]); |
| 31 | + } |
| 32 | + |
| 33 | + const result: number[][] = []; |
| 34 | + |
| 35 | + for (let r = 0; r < m; r++) { |
| 36 | + for (let c = 0; c < n; c++) { |
| 37 | + if (pacific[r][c] && atlantic[r][c]) { |
| 38 | + result.push([r, c]); |
| 39 | + } |
| 40 | + } |
| 41 | + } |
| 42 | + |
| 43 | + return result; |
| 44 | +} |
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